Foreign media organisations cannot report freely from Tibetan areas, so it is difficult to confirm facts from the area.

“Local officials exercised restraint during the riot and repeatedly told the rioters to abide by the law,” Xinhua quoted an official with the prefectural government as saying.

“Police were forced to fire warning shots and put down the violence,” the official added.

A UK-based activist group said eight people had been killed in the incident – including at least three women and one monk.

Matt Whitticase of the Free Tibet Campaign said Tibetan exiles in India confirmed that monks had marched on government buildings after two of them were arrested for having pictures of their spiritual leader, the Dalai Lama.

More than 350 monks demanded their release and were joined by about 400 lay people, he said.

Security forces opened fire after the demonstration had begun to disperse, he said.

Chinese authorities have repeatedly blamed the Dalai Lama, who lives in exile in India, for stirring up unrest. The Nobel Peace Prize laureate denies the accusations.